The interactive control described above is an indispensable function for reproduction apparatuses in receiving a user operation on selection of title and chapter to be reproduced, a reply to a quiz question, and the like, and is widely known to be realized on DVD reproduction apparatuses. The interactive control by a DVD reproduction apparatus is an application of OSD (on screen display) technology by which a button being a character string attached to a graphics is displayed on a screen, and the color of a frame of the button is changed according to a user operation. Such color change enables a user to intuitionally understand which button on the interactive display is in a selected state.
A disadvantage of the interactive control on a DVD is that there is hardly any factor for amusement. Specifically, users hardly find it amusing during operation of the DVD interactive control. In view of such criticism, animation display of buttons is attempted on the interactive display of a BD-ROM (Blu-ray disk prerecorded format) whose standardization is underway. To be more specific, in the interactive display presented by a BD-ROM, each button is presented in a form of original animation, and is overlayed with a scene of a movie, which is the main video image. In addition, the content of this animation display changes according to a user operation. When such an animation display is used to represent a character appearing on a movie work, a user can change the expression and action of the character by his operation directed to the interactive display. Such a kind of animation enables creation of interactive display by which even a child is amused.
However, the animation display for buttons incurs a large amount of decoding load, and so there is a problem that a waiting time, until an initial display of the interactive display is realized, becomes long. For example, assume that an interactive display such as shown in FIG. 1 is overlayed with a scene of a movie work. This interactive display has four buttons, each of which has three states: normal state; selected state; and active state. Also assume a case in which each state of button is presented in 2-3 seconds of animation display. Even if one page of graphics data is displayed at intervals of 5 frames in an image signal, about 30 pages of graphics data are required to realize 2-3 seconds of animation. Not only that, since there are three states for a button (normal state, selected state, and active state), there will be total of 90 pages (3*30) of graphics data. So as to dispose four buttons on an interactive display, it requires decoding of 360 pages (4*90), which is an enormous amount of graphics data. Decoding load for one page of graphics data is light. However, it takes about dozens of seconds so as to decode several hundreds of pages of graphics data. Even for a purpose of making amusing interactive displays, it is too much to keep users waiting dozens of seconds to display each interactive display, which deserves users' criticism.